The considerable increase in the cost of fossil energy sources since 1973, and especially that of oil, has greatly helped drive up the price of ethylene, whereas at the same time acetylene manufactured initially from calcium carbide or by electric arc could have hoped to profit from the relative low price of electric energy of nuclear origin. Despite the following optimistic assumption: (a) mean growth rate of oil prices (in constant 1982 R, currency) of 7% per year, (b) increase in that of coal limited to 3 % per year, (c) electric power permanently available at 5 to 10 French centimes per kWh, (d) unit production capacity of acetylene of about 300 000 t/year, comparable to that of ethylene, it appears impossible for acetylene to rival ethylene before the year 2000. Only vinyl chloride, manufactured from acetylene in large units with a considerable scale factor, could do so, provided that electricity could be supplied constantly at 0. 10 French francs per kWh. This point does not take into consideration the remodeling of current petrochemical processes for producing the second-generation chemicals. If these were to be manufactured from acetylene, installations having an entirely different design would have to be created. Whereas in 1975 electric-arc processes for producing acetylene from naphtha appeared more economical than the calcium-carbide route, the opposite situation is now seen as the resuit of the increases in oil prices that have occurred since then.